Vitamin D3 Promotes Not Motor Coordination but Motor Skill Learning without Influence on Muscle Function.

Although motor coordination or motor skill learning are improved by taking vitamin D in the animal experiment, muscle function have not been estimated. Here we examined the effect of vitamin D3 administration on motor coordination and motor skill learning, muscle strength, and muscle volume in mice fed a vitamin D deficient diet. In mice fed a vitamin D deficient diet, serum calcium and 25(OH)D3 concentrations were measured. We then conducted Rotarod test, beam walking assay, micro-CT analysis, and forelimb grip strength test. Administration of vitamin D3 elongated the retention time in the Rotarod test in a time dependent manner. In contrast, the time to reach a beam goal box in beam walking assay was not changed in mice administered with vitamin D3, compared to the control. Oral administration of vitamin D3 did not affect muscle strength nor muscle volume. Oral administration of vitamin D3 promotes not motor coordination but motor skill learning and does not affect muscle function.

The Association between Atherosclerotic Disease Risk Factors and Serum 25-Hydroxyvitamin D Concentration in Japanese Subjects.

Recent studies have described that vitamin D deficiency/insufficiency is associated with hypertension, insulin resistance, and dyslipidemia, which are major components of metabolic syndrome causing atherosclerosis. Therefore, we investigated the relationship between serum 25-hydroxyvitamin D [25(OH)D] concentration and atherosclerotic disease risk factors in healthy Japanese adults. In the present cross-sectional study, 1,177 subjects (348 males and 829 females) aged 20-72 y living in Japan (34.7-35.0ºN) were evaluated for vitamin D status by measuring serum 25(OH)D concentration. Atherosclerotic disease risk factors were defined as the presence of two or more of the following three risk factors: high blood pressure, dyslipidemia, and hyperglycemia. The percentages of vitamin D deficient and insufficient subjects were 33% and 46% in males and 59% and 32% in females, respectively. Subjects with atherosclerotic disease risk factors were significantly older and had higher BMI than those without it in both sexes. Male subjects with atherosclerotic disease risk factors had significantly lower physical activity and serum 25(OH)D concentration than those without it. In a logistic regression analysis adjusted for confounding factors, serum 25(OH)D concentration showed a significant inverse association with risk factors of atherosclerotic disease in males (OR=0.951, 95%CI: 0.906-0.998), but not in females. A covariance structure analysis also suggested that serum 25(OH)D level has a direct association with risk factors of atherosclerotic disease. In conclusion, we have demonstrated that low serum 25(OH)D level is a significant factor for increased atherosclerotic disease risk factors in males.

Vitamin D Status in Japanese Young Women in 2016-2017 and 2020: Seasonal Variation and the Effect of Lifestyle Including Changes Caused by the COVID-19 Pandemic.

Avoidance of sunlight and self-restraint due to the COVID-19 pandemic may contribute to reduced vitamin D status. This study provides comparable data on vitamin D status in Japanese young women and assesses the effect of lifestyle, including changes caused by the COVID-19 pandemic, on vitamin D status. In study 1, 39 young healthy Japanese women aged 21-25 y were recruited from May 2016-June 2017. Serum 25-hydroxyvitamin D (25OHD) concentration and diet and lifestyle information were obtained from participants each month (n=124). In study 2, using the same parameters as study 1, young women aged 21-23 y (n=10) were recruited in September 2020. In the results of study 1, we found the frequencies of vitamin D deficiency (25OHD<20 ng/mL) in spring, summer, fall, and winter were 90.5%, 62.5%, 81.5%, and 91.3%, respectively. The substantial difference of serum 25OHD concentration was obtained in spring (Δ3.6 ng/mL) and summer (Δ5.1 ng/mL) depending on the frequency of sunscreen use (0-2 d/wk, 3-7 d/wk). In study 2, serum 25OHD concentration in September 2020 was extremely lower than in September 2016 (13.2 ng/mL vs. 21.7 ng/mL). The number of days spent outside in 2020 decreased drastically compared with 2019. In conclusion, vitamin D deficiency was highly common in Japanese women in their early 20s, and frequent sunscreen use contributed to low vitamin D status. Moreover, because the decrease in days outside due to the COVID-19 pandemic obviously resulted in a decline in vitamin D status, both appropriate sunbathing and increased dietary vitamin D intake are recommended to young women.

Comparison of Vitamin D and 25-Hydroxyvitamin D Concentrations in Human Breast Milk between 1989 and 2016-2017.

BACKGROUND: Breast milk is considered the optimal source of nutrition during infancy. Although the vitamin D concentration in human breast milk is generally considered poor for infants, vitamin D in breast milk is an important source for exclusively breastfed infants. Increases in vitamin D insufficiency and deficiency in lactating mothers may reduce vitamin D concentrations in breast milk. This study aimed to compare vitamin D and 25-hydroxyvitamin D (25OHD) concentrations in breast milk collected in 1989 and 2016-2017 and simultaneously analyze them with liquid chromatography-tandem mass spectrometry (LC-MS/MS); the association between the lifestyle of recent lactating mothers (2016-2017) and vitamin D status in human breast milk was also evaluated. METHOD: Lactating mothers were recruited from three regions of Japan in 1989 (n = 72) and 2016-2017 (n = 90), and milk from 3-4 months was collected in summer and winter. The samples were strictly sealed and stored at -80℃ until measurement. Breast milk vitamin D and 25OHD concentrations were analyzed by LC-MS/MS. Vitamin D intake, sun exposure, and sunscreen use of the lactating mothers in 2016-2017 were assessed. RESULTS: Both vitamin D and 25OHD concentrations in breast milk were higher in the summer regardless of the survey year. Significantly lower vitamin D and 25OHD concentrations were observed in 2016-2017 compared with 1989 in summer, but no survey year difference was observed in winter. The stepwise multiple regression analyses identified season, daily outdoor activity, and suntan in the last 12 months as independent factors associated with vitamin D3 concentrations. CONCLUSION: The results suggest that low vitamin D status in recent lactating mothers may have decreased vitamin D and 25OHD concentrations in breast milk compared with the 1980s. These results are helpful for developing public health strategies to improve vitamin D status in lactating mothers and infants.

Oral Supplementation of the Vitamin D Metabolite 25(OH)D3 Against Influenza Virus Infection in Mice.

Vitamin D is a fat-soluble vitamin that is metabolized by the liver into 25-hydroxyvitamin D [25(OH)D] and then by the kidney into 1,25-dihydroxyvitamin D [1,25(OH)2D], which activates the vitamin D receptor expressed in various cells, including immune cells, for an overall immunostimulatory effect. Here, to investigate whether oral supplementation of 25-hydroxyvitamin D3 [25(OH)D3], a major form of vitamin D metabolite 25(OH)D, has a prophylactic effect on influenza A virus infection, mice were fed a diet containing a high dose of 25(OH)D3 and were challenged with the influenza virus. In the lungs of 25(OH)D3-fed mice, the viral titers were significantly lower than in the lungs of standardly fed mice. Additionally, the proinflammatory cytokines IL-5 and IFN-γ were significantly downregulated after viral infection in 25(OH)D3-fed mice, while anti-inflammatory cytokines were not significantly upregulated. These results indicate that 25(OH)D3 suppresses the production of inflammatory cytokines and reduces virus replication and clinical manifestations of influenza virus infection in a mouse model.

A simple questionnaire for the prediction of vitamin D deficiency in Japanese adults (Vitaimn D Deficiency questionnaire for Japanese: VDDQ-J).

Vitamin D deficiency (VDD) is associated with an increased risk of various diseases. Serum 25-hydroxyvitamin D [25(OH)D] concentration is the best marker for vitamin D status and its concentration < 20 ng/mL indicates VDD. However, its measurement is not easily applicable for the evaluation of vitamin D status in the general population because of its cost. Therefore, we aimed to develop a simple questionnaire for easily identifying the risk of VDD. From the total sample (649 healthy subjects aged 19-70 years), 434 and 215 subjects were randomly assigned to the derivation and the validation cohort, respectively. Prediction model for VDD was developed by backward logistic regression analysis. The regression ß coefficients of the significant predictors were transformed into integral numbers and used for the individual score. These individual scores were summed to calculate the total risk score (VDD questionnaire for Japanese score: VDDQ-J score). VDD was present in 54.1% of the total subjects. The model for the prediction of VDD consisted of 7 predictors. Areas under the curve were 0.78 and 0.75 in the data set of internal validation and of the external validation, respectively. The cutoff value was determined to be 31 points (range 0-54) with the sensitivity/specificity and positive predictive value/negative predictive value of 61%/79%, and 81%/57%, respectively. Our VDDQ-J score is easy to answer by the wide range of subjects, and well predicts VDD. This risk score would be useful to identify subjects at risk for VDD both in clinical and epidemiological settings.